The treatment with percutaneous drug administration generally involves drugs in the form of a solution or ointment being applied to the skin to enable the drugs to be absorbed within their affected area. Although the absorption of the percutaneously applied drug is accomplished primarily through diffusion, the natural biophylaxic functions of the skin to prevent foreign matters such as medicines, microbes, and viruses from penetrating into the human body prevent most of the medicine from being absorbed. Furthermore, the absorption rate of the medicines that are successfully absorbed is made quite slow. There have been devised various methods for improving the absorption rate of drugs for the endermatic absorption.
One of the methods for improving the drug absorption rate is iontophoresis ( iontophorese ) described, for example, in MORIMOTO's "Development of TTS drugs in the United States," Therapeutic Research, Vol. 10, No. 3, 1989, pp. 169(889)-pp. 180(900).
Iontophorese, namely iontophoresis, is a sort of electrotherapeutic method for introducing percutaneously or transmucosally predetermined medicines into a living body without pain by use of a direct current (refer to Nanzando's Medical Dictionary, published Apr. 10, 1974). As shown in FIG. 9, by providing electrodes 32a and 32b onto drug containers 31a and 31b and by providing the DC potential difference between respective electrodes 32a and 32b, charged substances are transferred to within the skin A along with lines of the electrodynamic force. That is, positively charged substances will be attracted to the negative electrode 32b side, and negatively charged substances to the positive electrode 32a side. While transferring, the medicines will be absorbed into the bloodstream and transferred to whole body. Iontophoresis has the advantage of drug absorption being promoted, since, in addition to the effect of the concentration gradient, the drug may also be absorbed by the effect of electrophoresis.
As iontophorese sends an electric current through skin, if the resistance of the skin is increased, higher voltage must be applied to provide a sufficient current. This may cause low-temperature burning of the skin or patient discomfort. These problems may be avoided by lowering the applied voltage. In this case, however, the reduced amount of drug transfer by electrophoresis may not sufficiently increase the absorption rate of the drug. Furthermore, skin resistance may vary significantly with factors such as location, ambient conditions, perspiration, bloodstream, age and so on. As the quantity of the administered drug may differ among patients even when the same voltage is applied, this creates the disadvantage of stable drug administration being difficult to achieve.
The sampling of such humor as blood is performed for analyzing the patient's condition before treatment or for generic lab-testing. Usually, the sampling of body fluid is performed by using a syringe and a needle, which may cause pain as well as infection of the microbes. To overcome these difficulties, an attempt at aspirating body fluid out of body by applying heavy negative pressure onto the skin has been made. However, it is disadvantageous in that this attempt causes the subject pain when sucking and may leave a suction mark for a few days. Further problems are raised in that a large-scale device for generating the negative pressure may be required and its operation may be complicated.
Another method for sampling humor by electrophoresis as an application of above-mentioned iontophoresis is disclosed in "Skinside Out," Scientific American, November 1991, pp. 93-94. This attempt presents a problem in that a sufficient quantity of body fluid cannot be extracted using only electrophoresis. Although it may be possible to increase the current to extract more sampled humor, such problems as low-temperature burning and electric shock may result.
In Japanese Unexamined Patent Publication No. HEI-3-170172, a drug administration device using iontophoresis with the utility of ultrasonic wave vibration is disclosed. This drug administration device described in said Unexamined Patent Publication has been devised for administering drugs, and not for sampling body fluid. In addition, this drug administration device provides only one ultrasonic wave signal element on one of the electrodes for applying iontophoresis.
In International Patent Publication No. WO 91/12772, the use of iontophoresis technology after the irradiation of the skin with ultrasonic waves for the percutaneous drug administration is disclosed. There is not disclosed a point of simultaneously performing the ultrasonic wave irradiation method and iontophoresis method.
The object of the present invention is to provide a drug administration and humor sampling unit and its apparatus, which enables the drug absorption rate to be increased with lower applied voltage and is able to sample a sufficient quantity of body fluid with lower applied voltage.